The present invention relates, in general, to socket welded fittings and, more particularly, the present invention relates to a positive gapping device for socket welded fittings.
It is generally well known throughout the industry that if a pipe section is placed in a socket tightly against the shoulder during a welding operation that residual stresses are produced due to the heating and cooling of the weld joint. To eliminate this problem a gap is typically specified in order to provide a space between the socket shoulder and the end of the pipe section so as to eliminate this problem by providing room for expansion.
In order to ensure that this gap truly does exist, a washer with axial movement has been developed and has been used in the industry. Although to some extent the washer does solve the gapping problem, several other additional problems are also present and continue to exist with this type of washer system. First, there is the additional cost that is related to the manufacturing of the extra component that is needed in this system. Further, there is no way to ensure that this washer, or that such gap, was indeed in place prior to welding because after the fittings are welded together it is too late. Unless the presence of the washer is noted and identified before the welding operation, after the weld is completed there is no way of going back and checking.
Once the welding operation is completed there is no visual indication as to whether a spacer was used or not. Thus, there is no guarantee that a gap was indeed present. The gap is necessary to relieve the compressive stresses on the pipe that are produced during welding and which result in tensile stresses on the weld during service. These stresses result in lower weld life.
The present invention provides a positive gapping device for socket welded fittings. The positive gapping device comprises a socket fitting having at least one recessed area for receiving a pipe section that is engageable with the recessed area of the socket fitting. It further includes a gapping means disposed on one of a surface of the recessed area of the socket fitting facing an end of such pipe section and an end of such pipe section for engagement with such socket fitting. The gapping means providing a space between the socket fitting and such pipe section for reducing residual stresses that result from a welding operation.
Another embodiment of the invention provides a positive gapping device for socket welded fittings wherein an identification means is provided on an exterior surface on one of the socket fitting and such pipe section for identifying one of the socket fitting and such pipe section as having a proper gapping means disposed therein.
It is, therefore, one of the primary objectives of the present invention to provide a gapping means for socket welded fittings.
It is also an object of the present invention to provide a failsafe positive gapping means.
Additionally, it is an object of the present invention to provide a visual indication of a properly prepared socket weld fitting that is evident after the weld is completed.
Further, it is an object of the present invention to provide a gap that is machined into the fitting without the need for an additional component.
Yet, still another object of the present invention is to provide a gapping means that is relatively inexpensive to manufacture.
These and other objects and advantages of this invention will become apparent after a full reading of the following detailed description, particularly, when read in conjunction with the attached drawings as described below and the appended claims.